Solid-state lighting devices have many uses in residential and commercial applications. Some types of solid-state lighting devices may include laser diodes and light-emitting diodes (LEDs). Ultraviolet (UV) solid-state lighting devices may be used to curing photosensitive media such as coatings, including inks, adhesives, preservatives, etc. Solid-state lighting devices may be driven by a switching regulator.
For example, the switching regulator delivers a desired current based on a requested irradiance or illuminance output of the solid-state lighting devices. Some solid-state lighting systems include a feedback circuit that outputs an error voltage based on a comparison of a feedback voltage received from the solid-state devices with a reference voltage. The error voltage is then used to adjust the output of the switching regulator. Typically, the reference voltage is set based on the requested output of the solid-state devices. For example, when the requested output is lower, the reference voltage is lower and as the requested output increases, the reference voltage is increased.
However, the inventors have recognized potential issues with such approaches. As one example, a startup time for the switching regulator to achieve the desired current is dependent on the requested output of the solid-state lighting devices. For example, if the requested output is higher (e.g., 100%), the startup time for the switching regulator is less (e.g., 2 milliseconds); however, if the requested output is lower (e.g., 10%), the startup time for the switching regulator increases (e.g., 20 milliseconds). The delay in the startup time at lower requested outputs is due to a delay in a charging time of the capacitors in the feedback circuit. For example, during startup, if the requested output is lower, the reference voltage is set lower, which causes the capacitors in the feedback circuit to be charged by an associated operation amplifier at a lower current. Consequently, it takes a longer time to generate the error voltage that is required for energizing the switching regulator to obtain the desired regulator output. Hence, the delay in the startup time of the switching regulator increases as the requested output of the solid-state devices decreases.
In one example, the issues described above may be addressed by a lighting system for operating one or more light emitting devices, comprising: one or more light emitting devices; a switching regulator including a regulator output in electrical communication with the one or more light emitting devices; an error amplifier including a first input, an second input, and an error output, the error output in electrical communication with the switching regulator via a pulse-width modulation generator; and a controller including non-transitory instructions to adjust the first input of the error amplifier to a first higher voltage in response to a startup of the lighting system. In this way, the delay in startup time for the switching regulator may be reduced.
As an example, when the lighting system is switched to an ON state from an OFF state (that is during startup of the lighting system), the reference voltage input into an error amplifier of the lighting system is set to a first higher voltage independent of the requested output of the lighting system. The first higher voltage may be based on a maximum irradiance or illuminance capability of the lighting system (e.g., 100% irradiance). By setting the reference voltage of the error amplifier at the first higher voltage, the error amplifier is forced to charge the capacitors in the feedback circuit with a higher current. Consequently, the output of the error amplifier increases at a faster rate and hence, the delay in generating the desired error voltage for energizing the switching regulator during startup is reduced. Upon obtaining a desired output of the switching regulator (the desired output based on the requested output of the lighting system), the reference voltage of the error amplifier is adjusted based on the requested output of the lighting system. For example, if the requested output of the lighting system is 10%, at startup, the reference voltage is set to a first higher voltage, the first higher voltage based on 100% requested output. Simultaneously, the output of the switching regulator is monitored, and when the output of the switching regulator reaches a desired output, where the desired output is based on the requested output (that is, 10%), the reference voltage is decreased from the first higher voltage (based on 100% output) to a second voltage (based on the 10% requested output).
In this way, accelerated startup of the switching regulator driving the lighting system may be achieved independent of the requested output of the lighting system.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.